Preheat the oven to 425°F. Lightly grease a 9x13 casserole dish.
Heat the olive oil in a large skillet over medium heat. Add the beef along with some salt and pepper. Brown the meat, using a spatula to break it up into smaller pieces as it cooks, about 5 minutes (it’s ok if it’s not completely cooked through at this point since it will have more time in the next step). Drain away any excess fat.
Stir in the onions and cook until softened, about 5 minutes.
Remove from the heat and stir in the garlic powder, tomato sauce, tomato paste, pickles, pickle juice, and mustard. Taste; add salt and pepper if desired.
Transfer the mixture to the prepared casserole dish, pressing it evenly into the pan with the spatula. Top with the cheddar cheese.
Roll out the biscuit dough on a lightly floured surface until it’s about 1/2-inch thick. Use a 3 1/2 inch round cutter (or similar) to cut the biscuits, rerolling the dough a couple times as needed. Cut each biscuit round into quarters.
Place the biscuits pieces evenly over the meat and cheese, then brush the tops with melted butter.
Bake until the biscuits are risen and golden brown, 18-20 minutes.